256 Professor Pictet on the Distribution of Fossils. 



how many important and interesting questions are connected 

 with the study of fossils. It will readily be understood how 

 it happened that naturalists, on perceiving, for the first 

 time, the results of this science, have been inclined to allow 

 their imagination to wander beyond the limits to which a 

 strict observation of facts ought to have confined them ; for 

 these facts, although not numerous enough to admit of suffi- 

 cient precision, were still adequate to shew the importance 

 of the laws which seemed to result from the study of them. 

 It is expedient, therefore, to point out, in this place, what 

 these generalisations are founded upon, to examine what is 

 true in them, and what false, and to discuss their real 

 limits. In the sequel, I shall first pass in review the laws, 

 that is, the general rules, which flow directly from the com- 

 parison of facts, and conclude by pointing out the theoretical 

 principles which have been devised, in order to explain the 

 succession of faunas. 



The principal laws* which it has been thought proper to 

 establish, may be reduced to five. These I shall examine in 

 succession. 



First Law. — The species of animals belonging to one geo- 

 logical epoch, have lived neither before nor after that epoch ; 

 so that each formation has its fossil species, and no species 

 can be found in tivo formations of a different age. This law 

 is one of those, the certainty and generality of which, I 

 believe the progress of science will shew more clearly 

 every day ; but it is not admitted by all geologists. Many 

 naturalists of high authority think that it is true in regard 

 to the greater number of species, but false in regard to some, 

 which, in their opinion, have passed from one epoch to an- 

 other ; and that, therefore, it is not general. 



The soluti(m of this question is of the highest interest for 

 palaeontology ; for on the manner in which we regard it, the 

 opinion which we may entertain as to the importance of the 

 applications of this science to geology, entirely depends. If 

 fossils are peculiar to certain formations, they characterise 



* I have here mentioned only the principal laws ; others exist which 

 have not been sufficiently proved, except in regard to particular classes 

 of animals. 



